Newtek does not have an IPS Tag. It is not necessary to have one unless you are a Registrar of co.uk domains.
If you would like to host your co.uk domain with us, there will be no need for an IPS Tag. The IPS Tags are only used when transferring the registration itself to another authorized co.uk registrar.
Hosting your co.uk domain with us is as simple as pointing the domain to our name servers, which does not require moving registrars. Unless you have a custom DNS, you will want to list our name servers with your registrar which can be found under Site Overview (under Site Admin) or in your Web Site Ready Email.